Artificial silk



Nov. 9, 1937. H. 'r. CLARKE ET AL 2,098,223

ARTIFICIAL SILK Original Filed March 4, 1931 jwuenf-omc IimaTClewlMbrLJMzbm atented ov. 9, 193'? OFFICE CIAL SILK Original application March 4, 1931, Serial No.

520,149. Divided and this 1934, Serial No. 731,916

6 Claims.

This invention relates to a process of producing synthetic filaments and yam'from cellulose acetate-butyrate containing 10%-30% and preferably about 15% of butyryl groups (figured as percent of the entire ester) and to the filaments and yarn so produced. This application is a division of our applications Serial Nos. 520,149 and 560,208, filed March 4, 1931, now U. S. Patent 1,969,454 and a continuation-in-part of our application Serial No. 179,177, filed March 28, 1927, now U. S. Patent 1,880,808.

It has been known heretofore to make synthetic yarn from regenerated cellulose such as viscose or from cellulose acetate but those materials have certain disadvantages which are overcome in the employment of a cellulose acetate-bu'tyrate, such as we employ for the making of synthetic yarn.

The synthetic yarn of our invention has a resistance to the deleterious efiect of washing materials which is superior to that of any synthetic yarn known prior to our invention. The lustre and life of our synthetic yarn continues thru the entire period during which it is normally used, for instance, in wearing apparel or the like.

We have found that synthetic yarn made from cellulose acetate-butyrate containing more than 10% and preferably about 15 of butyryl groups (figured as percent of the entire ester) is highly resistant to the action of boiling water, soaps and commonly employed washing alkalies.

For example, if a cellulose acetate fabric be boiled in soapy water (or clear water, for that matter) the fabric will be delustered, to a degree depending on the severity of the conditions. On the other hand, a cellulose acetate-butyrate fabric such as we have discovered may be treated under similar severe conditions without having its beauty and brilliance impaired. We have made possible, wash garments of synthetic yarn whose life and beauty will not be impaired by laundering operations, even as severe as those carried out in commercial laundries.

Previously known synthetic yarn when wetted is greatly reduced in strength, so that the laundering of thefabrics produced therefrom or even dampening due to perspiration or rainfall greatly weakens the threads, and breaking with accompanying unraveling may occur. We have found that the threads of synthetic yarn made from cellulose acetate-butyrate of a butyryl content greater than 10% (figured as percent of the entire ester) have a wet strength considerably more than that of ordinary synthetic yarn so that the danger of breaking of threads is reduced to a minimum. As a consequence, garments made of our synthet.

application June 22,

1c yarn may be handled when wet without the great danger of breaking of thread with subsei uent unraveling and ruin of the garment. This feature is especially valuable in goods of a fine, lacy nature.

Another advantage of employing cellulose acetate-butyrate of more than 10% butyryl content is that a greater variety of solvents may be employed in the production of the filaments than is possible with cellulose acetate.

This allows the selectionof the solvent best suited for the filamenting of the cellulose acetatebutyrate. For example, acetone is the solvent commonly employed for filamenting cellulose acetate. However, in the case of cellulose acetatebutyrate of more than 10% butyryl, the use of ethylene chloride-methanol (9:1) is preferred, although other proportions or other lower aliphatic alcohols may be used. In the case of cellulose acetate-butyrate having a butyryl content of at least 15% or more, so that the ester is soluble in ethylene chloride per se, thatliquid is eminently suitable for the filamenting of the cellulose acetate-butyrate. Ethylene chloride is less expensive than acetone and also gives a more brilliant product, due, probably, to the fact that it is not afiected by moisture so that any tendency toward dullness from the presence of moisture is eliminated. Also, any moisture which may be present would distill azeotropically with the ethylene chloride upon filamenting in the, dry-spinning or evaporating process which we prefer to employ in the present case.

As is well known in the cellulose acetate industry, the cellulose acetate to be suitable for products such as filaments must be hydrolyzed usually to an acetyl content of about 38-40%. It is also well known that the tri- .or fully esterified esters of cellulose exhibit a greater resistance to wetting than esters which have been hydrolyzed. This naturally follows as it is common knowledge that, other things being equal, the more hydroxyl groups in a molecule, the more compatible the molecule becomes to water. In our present invention either the fully esterified cellulose acetate-butyrate or the hydrolyzed ester' may be employed to produce filaments. For example, if a filament is desired which is highly resistant to wetting, the fully esterified ester is employed.

Obviously, such filaments will also be resistant to a certain extent to dye baths and, consequently, to obtain a product which is to be dyed a partially hydrolyzed ester is more suitable although by no means necessary. In cases where a mixture of light threads is desired in a dark fabric, some threads of the fully esterified ester may be incorporated in a fabric of the partially hydrolyzed ester and the whole, upon being subjected to a dye bath, will give a dark fabric having light threads therein. Obviously, a light fabric having dark threads incorporated therein may be made by using the fully esterified ester for the body of the fabric and incorporating threads of the partially hydrolyzed ester therein. Various other decorative and useful eifects may likewise be produced.

The accompanying diagrammatic drawing illustrates by way of example one form of apparatus in which our process may be embodied.

Figure 1 is a side elevation of a unit of a spin ning machine which may be employed in producing synthetic yarn according to our process.

Figure 2 is a section at right angles to Figure 1 taken through the line 2-2 of Figure 1.

I represents the pipe or manifold through which the cellulose ester solution or dope may be supplied by means of valve 2 or pump 3 to the filamenting apparatus. The dope or solution passes through a. candle filter 4 which is enclosed in a chamber 5 heated by means of hot ,water coils 6 or other well known heating means as described and claimed in Stone application Serial No. 560,191, filed August 29, 1931. This chamber 5 is separated from the spinning cabinet 9 by a partition which may be well insulated if desired. In fact it is preferred to insulate the entire chamber 5.

If the temperature at which it is desired to keep the candle filter should be considered unimportant, obviously the hot water coils may be omitted and if some heat is desired around the candle filter, the heated air from below may be allowed to surround it. It is, however, desirable as described in the above Stone application to maintain the candle filter at a temperature somewhat above that of the air of the spinning chamber. The candle filter 4 is connected with a spinnerette I to form the dope as it comes through the candle filter into filaments of a desired size and deliver them into the heated air present in the spinning cabinet 9. The cabinet 9 is provided with an air inlet l9 at its lower end in which is located a steam pipe IS with heat dissipating fins II, which heats the incoming air. Obviously other means of heating the incoming air than that shown may be employed, the steam pipe with heat dissipating means located in the bottom of the cabinet is shown merely as an example of one means which may be employed to heat the incoming air. The solvent laden air in the upper portion of the cabinet may be removed through the outlet 8 which leads to a solvent recovery apparatus, the outlet 8 being preferably located a little below the top of the spinning cabinet.

After the dope is forced through the spinnerette 1, into the heated air, the solvent evaporates from the group of so-formed filaments which are grouped together as a thread or yarn. The thread passes over the guide roll II (or if desired a fixed guide may be employed) and out of a'small aperture in the cabinet to the draw roll I2 from whence it is conducted to the spinning pot or bobbin l5, through the guide M, to assure uniform winding of the thread. The spinning pot'or bobbin is rotated by means of a motor, a tape or a belt drive or any other suitable device which may also be employed for operating the guide M in any suitable manner desired. A waste roll I3 is provided below the draw roll 12 to collect any threads which might drop from the draw roll.

It is to be understood that instead of a spin ning pot and roll winding, any other method such as cap spinning, may be employed to collect the thread or yarn after its formation.

The above example illustrates one means of producing filaments from a cellulose acetatebutyrate dope and forming yarn therefrom. Instead of evaporative spinning, other methods of filamenting the dope such as wet spinning which comprises the running of the dope from a fine orifice or series of orifices into a precipitating liquid may be employed.

The following is given as a specific example of our process of producing synthetic yarn from cellulose acetate-butyrate containing more than 10% of butyryl groups (figured as percent of the entire ester).

Cellulose acetate-butyrate prepared in accordance with method described in U. S. Patent No. 1,800,860 and application Serial No. 520,149 and hydrolyzed for approximately hours in accordance with the hydrolysis method described in Malm and Fletcher application Serial No. 551,546

and having a content of 27.2% acetyl and 17.1% butyryl, two free hydroxyl groups per 24 carbon atoms, and a 90% precipitation value in 70% acetone was dissolved in ethylene chloride-methanol (9:1) in the proportion of about 5 parts 65 C. The temperature at the bottom of the I cabinet was maintained at 58 C. by-incoming heated air and the heating coils and the withdrawal temperature of the solvent-laden air was found to be 48-53 C. when air was passed through the cabinet at the rate of 20 cu. ft. per minute. A thread of denier was thus formed. Obviously, if the threads are larger it'will be advantageous to pass air through the cabinet at a more rapid rate.

The thread produced was found to have a wet strength of .98 gm. per denier as compared with a Wet strength of .65-.'75 gm. per denier for cellulose acetate. On comparing threads of 150 denier a cellulose acetate filament of this denier would have a wet strength of only about 97.5 112.5 gms. while the cellulose acetate-butyrate filament of this denier prepared as described would have a wet strength of approximately 147 gms. It was also found to have a resistance to the delustering action of boiling water superior to that of any synthetic yarn which is manufactured at the present time, including that made from cellulose acetate. This test was carried out by exposing the various samples to boiling distilled water for 60 minutes with stirring after which they were removed from the water, dried and their relative resistances to delustering compared. That prepared from cellulose acetatebutyrate had substantially the same lustre as it had originally before the boiling operation.

The cellulose acetate-butyrate synthetic yarn, as prepared above, was also compared with samples of synthetic yam made from other cellulose esters, including cellulose acetate, as to the de gree of hydrolysis by an alkaline bath, such as it would be contacted with in laundering operations. This test was carried out by placing the samples which were in the form of hanks of yarn in a 30:1 bath containing 1% potassium hydroxide and 3% soap (both based on the dry weight of the yarn) at 80 C. for 40 minutes. The samples were removed from the bath and rinsed and to determine the degree of hydrolysis caused by the alkali they were exposed to a dyeing bath containing a direct cotton dyestuff. The color density of the cotton dye on the yarn is indicative of the degree of hydrolysis of the sample. The difierences in color density in this trial were very pronounced, the cellulose aoetate-butyrateyarn showing much greater resistance to the hydrolyzing action of the alkali than did the other samples. Thus, in spite of the fact that the development of cellulose acetate yarns has been going on for years, yet the yarn made from cellulose acetate-butyrate exhibits those characteristics which have been desired for years in the synthetic yarn art.

Instead of the ethylene chloride-methanol (9:1), this mixture of solvents in other proportions or other solvents such as acetone, acetonealcohol, ethylene chloride with'or without additionsof alcohol or in fact almost any volatile organic solvent in which the ester is soluble may be employed in the production of synthetic yarn fro-m cellulose acetate-butyrate of more than 10% butyryl content. If desired a higher boiling liquid might be added such as butyl or amyl alcohol however higher temperatures or longer times may be necessary to evaporate off the solvent in an evaporative spinning process in which a higher boiling liquid is added.

Obviously, in the foregoing example, the fully esterified ester may be employed instead of the partially hydrolyzed ester and, as pointed out previously, the filaments formed will be more resistant to water and dyes than those formed from the cellulose acetate-butyrate which has been partially hydrolyzed.

As pointed out in our co-pending application No. 528,966 various plasticizers such as triphenylor tricresyl-phosphate may be incorporated with the cellulose acetate-butyrate which-we employ for making synthetic yarn when threads of a more pliable nature are desired.

The synthetic yarn produced from cellulose acetate-butyrate even showed properties superior to a synthetic yarn prepared from cellulose acetate-propionate. For instance, although the wet strength of a cellulose acetate-propionate thread was comparatively high, being .89 gm. per denier, the wet strength of the cellulose acetatebutyrate yarn was found to be as high as .98 gm. per denier, constituting an increase in wet strength of more than 10%.

The cellulose acetate-butyrate filaments also showed even greater resistance to boiling water and to the action of soaps and alkalies than did filaments of cellulose acetate-propionate and possess those properties which are at present greatly desired in synthetic yarn, namely, high wet strength and good resistance to the delustering action of the materials commonly employed in laundering, thus giving great promise of being the cellulose ester synthetic yarn of the future.

Other obvious modifications of the present process will be apparent to those skilled in the art and are within the contemplation of this invention.

The term synthetic yarn used herein is intended to define a number of synthetic filaments grouped together in the form of a thread.

We claim as our invention:

1. Synthetic yarn comprising filaments of cellulose acetate-butyrate containing acetyl groups and having a butyryl content of at least 10%.

2. Synthetic yarn comprising filaments of cellulose acetate-butyrate containing acetyl groups and having a butyryl content of at least 3. Synthetic yarn comprising filaments of fully esterified acetate-butyrate containing acetyl groups and having a butyryl content of at least 10%.

4. Synthetic yarn comprising filaments of fully esterified cellulose acetate-butyrate containing acetyl groups and having a butyryl content of about 15%.

5. Synthetic yarn comprising filaments of partially hydrolyzed cellulose acetate-butyrate containing acetyl groups and having a butyryl content of at least 10%.

6. Synthetic yarn comprising filaments of cellulose aoetate-butyrate containing acetyl groups and having a butyryl content of 10-30%.

HANS T. CLARKE. CARL J. MAIM. 

